There are basically five principles of cavity preparation that you need to know when mastering the bench test. These principles answer why these cavity preparations has such forms, depth, convergence and angulation. This is a boring section, but if you take these principles into heart, you can make any cavity preparation on any tooth easily.
Outline Form and Initial Depth
Definition: Placing the preparation margins in the position they will occupy in the final preparation. In other words, this principle dictates the form of your cavity preparation basing on the curvatures of the fissures, depth, Isthmus width, and the marginal ridge.
Resistance Form
Definition: Features in which the tooth and the restoration will not fracture when the tooth is in function
Retention Form
Definition: Shape and Form of the cavity preparation that resists displacement or removal of the restoration by tipping or lifting forces.
Convenience Form
provides for adequate observation, accessibility, & ease of operation in preparing & restoring the tooth
Finishing
Further development,when indicated, of a specific cavosurface design & degree of smoothness or roughness